Method for treating onychomycosis

ABSTRACT

A method for treating onychomycosis without drilling a hole in a nail plate or without daily scraping of the nail, comprising topically administering to the afflicted nail of a mammal 
     i) a medicated device comprising salicylic acid or a salt, ester or mixture thereof in a plaster preparation, wherein said plaster preparation is attached to a carrier and the salicylic acid is present in the plaster preparation in an amount ranging from about 10 to about 80 percent (%) by weight of the plaster preparation; or 
     ii) a liquid preparation comprising salicylic acid or a salt, ester or mixture thereof in a film-forming liquid vehicle, and the salicylic acid is present in the liquid preparation in an amount ranging from about 6 to about 35% by weight of the liquid preparation.

This is a continuation-in-part application of U.S. patent application Ser. No. 07/961,282, filed Oct. 15, 1992, now abandoned.

BACKGROUND

Onychomycosis or tinea unguium (ringworm of the nails) is a chronic disease of the nails due to parasitic fungi. Onychomycosis can cause the nail to appear thickened and lusterless, and often causes nail discomfort. Also, the infected nail harbors a reservoir of pathogenic organisms which can spread to and reinfect other parts of the body, causing chronic diseases such as onychomycosis in other nails, athletes foot, foot dry skin and the like. Onychomycosis is prevalent throughout a large proportion of the population, with most of those afflicted from the ages of 40 years and older. To date, the United States Food and Drug Administration (FDA) has not approved any topical treatments for onychomycosis, either prescription or over-the-counter (OTC), due to the poor response of treatments evaluated. This poor response is partly because the nail is a difficult barrier for anti-fungal compounds to penetrate. In the Federal Register, Tuesday, Mar. 23, 1982, Part III Department of Health and Human Services, Food and Drug Administration, Topical Antifungal Drug Products for Over-the-Counter Human Use, Establishment of a Monograph reports: "Fungal infections of the . . . nails tend to be chronic. They respond poorly to topical therapy, partly because of the thickness of the nails . . . sites of infection provide inaccessible locations for fungi, thus drastically decreasing the penetration of topical antifungals. For this reason, OTC topical antifungals must be labeled that they are not effective for the treatment of ringworm of the . . . nails."

The research by Jacob Brem, "Treating Onychomycosis," The Lancet, Oct. 29, 1977, Vol 2., p 937 demonstrates the extreme measures taken by one researcher to penetrate the nail: ". . . five or six holes are drilled in the nail plate, in the form of a crescent . . . Anaesthesia is not necessary. However, the introduction of the needle is felt when the nail bed is reached . . . The holes are enlarged by dipping a round toothpick in dichloroacetic acid and drilling through the hole in the nail. When the acid reaches the nail bed a burning sensation is felt . . . A week later, five or six new holes are drilled . . . If necessary, more holes could be drilled and further applications of acid could be given."

In a similar manner, the book, "Diseases of the Nail" by V. Pardo-Castello, Thomas Books, Baltimore, Md., (1936), pp. 22-40 describes several treatments for onychomycosis, including the following: "Craik (43) has reported two cases treated with success by means of daily applications of a solution of 4 grams of salicylic acid in 45 c.c. of methylated spirit, after thoroughly scraping the nail. The cited reference, R. Craik, "A Simple Treatment of Ringworm of the Nails", Brit. M. J. Feb. 1920, p. 185 describes a procedure wherein a lotion containing salicylic acid was ". . . to be painted on after scraping [the finger nail] every night, and without scraping every morning, and to be used for three months or longer." Scraping a finger nail each day for three months or more has effect of thinning or completely removing the nail plate.

Avulsion or surgical approaches for treating onychomycosis have also been used. Infected nails are treated by surgically or chemically removing the nail and treating the exposed nailbed with topical antifungals. These treatments must be continued until the nail grows out, typically 6 months or more. Although the surgical approach generally results in cure rates significantly higher than those reported for topical treatments, most patients dislike undergoing surgery, which can result in permanent nail loss.

Clearly, there is a need to provide an effective method for treating onychomycosis in which salicylic acid or a salt, ester or mixture thereof can be applied topically to an afflicted nail, without the need to drill holes in the nail, scrape the nail daily for three months or more and/or avulse the nail. There is also a need to provide a method for treating onychomycosis through use of a medicated device or a film-forming liquid preparation which enables the salicylic acid to remain in contact with the nail, thus facilitating its penetration into the nail.

SUMMARY OF THE INVENTION

The present invention is directed toward a method for treating onychomycosis without drilling a hole in a nail plate and without daily scraping of the nail, comprising topically administering to the afflicted nail of a mammal:

i) a medicated device comprising salicylic acid or a salt, ester or mixture thereof in a plaster preparation, wherein said plaster preparation is attached to a carrier and the salicylic acid is present in the plaster preparation in an amount ranging from about 10 to about 80 percent (%) by weight of the plaster preparation; or

ii) a liquid preparation comprising salicylic acid or a salt, ester or mixture thereof in a film-forming liquid vehicle, and the salicylic acid is present in the liquid preparation in an amount ranging from about 6 to about 35% by weight of the liquid preparation.

Preferably the salicylic add is employed in a plaster preparation using self-adhesive rubber or acrylic-based plaster vehicle.

The present invention has the advantage of providing an easy-to-use method for treating onychomycosis in which the afflicted nail can be treated directly, as compared to indirect or systemic methods utilizing oral antifungal agents. By directly treating the afflicted nail, fewer side effects can be expected compared with oral antifungal agents. The present method can also provide for convenient, continuous delivery of the active ingredient (ie. salicylic acid) over the treatment period. When a medicated device is employed, the method can provide further advantages in that: i) a medicated device made of a plaster and/or its carrier can be constructed to occlude and hydrate the nail for assisting delivery of the active ingredient from the plaster and promote penetration into the nail, due in part, to the increased permeability of the nail; ii) a medicated device can retain the active ingredient in place despite rubbing or scraping of the medicated device against hosiery or the shoe; iii) a medicated device has little or no odors compared with solvent-based systems; iv) a medicated device can be easily applied by placing it in contact with a nail, and can also be easily removed by peeling it off when finished; and v) a medicated device can theoretically hold greater amounts of the active ingredient since it can be made thicker than a solvent-based lacquer application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a depicts a side view of medicated device 2 before its application to finger 8. Device 2 is made of plaster preparation 4 which is attached to carrier 6. Plaster preparation 4 contains salicylic acid or a salt, ester or mixture thereof in a plaster vehicle, such an an acrylic-based plaster vehicle. In this embodiment the the plaster preparation possesses self-adhesive properties so that the device can be adhered directly to nail 10 and/or nail fold 12 of finger 8 without the need for additional adhesive.

FIG. 1b depicts a perspective view of device 2 adhered directly to nail 10 and nail fold 12 of finger 8.

FIG. 2 shows a perspective view of medicated device 2 before its application only to the nail of toe 8. As in FIGS. 1a and 1b, device 2 is made of plaster preparation 4 and carrier 6. Alternatively, a bandage (not shown) could be used to further secure medicated device 2 to finger 8 or toe 8.

DETAILED DESCRIPTION OF THE INVENTION

Salicylic acid, salts or esters thereof can be employed as the active ingredient in the present method. Suitable salts include the sodium, potassium, calcium or magnesium salts thereof. Suitable esters include the C-1 to C-4 esters thereof, such as methyl salicylate. Other esters include salsalate (salicylsalicylic acid), the salicylate ester of salicylic acid. Most preferably the acid form is employed as the active ingredient.

The term "medicated device" refers to a combination of salicylic acid or a salt, ester or mixture thereof in a plaster preparation, wherein the plaster preparation is attached to a carrier.

The term "vehicle" broadly refers to any inert medium in which the active ingredient is administered, including but not limited to film-solvents, plasters, carriers or binders for the active ingredient.

The term "plaster" refers to any non-liquid vehicle which can be applied to the nail and which can hold the salicylic acid against the nail surface. Suitable plaster vehicles include plasters or preformed films based upon rubbers, acrylics, polyvinylalkylethers, gels or impregnated microporous membranes. Alternatively, the plaster could be combined with or formed into shape of an artificial or fake nail to improve cosmetic appearance.

The term "plaster preparation" refers to a preparation of salicylic acid or a salt, ester or mixture thereof in a plaster vehicle. The salicylic acid in a plaster preparation is employed in an amount effective to penetrate the nail to reduce and/or control onychomycosis. Such amounts can range from about 10 to about 80 percent salicylic acid by weight of the preparation, preferably from about 15 to about 60 percent by weight of the preparation, more preferably from about 20 to about 40 percent by weight of the preparation, most preferably about 40 percent by weight. Preferably, the plaster preparation is self-adhesive, ie. self-adhering to the nail, although any suitable means such as a bandage could be used to hold the plaster against the nail surface.

In the most preferred embodiment, the plaster preparation containing salicylic acid and the plaster vehicle is attached to a carrier to form a medicated device. In the medicated device, the carrier can impart occlusive properties and dimensional strength to the plaster preparation. The carrier can also provide dimensional stability to the plaster preparation against disintegration and/or tearing by external forces, such as shear forces exerted on the plaster from normal handling or from rubbing of the toenail against the shoe, sock or stocking. The carrier can be selected from a wide range of materials, especially those which can promote occlusion and hydration of the nail, such as a resin-impregnated woven cloth, flexible polyvinyl chloride film or a flexible polyester film. However, the plaster preparation can be designed to be highly occlusive without the need for the carrier to possess substantial occlusive properties. The carrier can be attached to the plaster preparation by lamination techniques, by coextrusion or by bonding the carrier onto the plaster preparation using adhesives. The carrier also serves the function of directing the salicylic acid toward the nail, thus minimizing its dissipation or dispersion into the shoe interior. The medicated device can be formed into any shape suitable for administering the salicylic acid to the nail. Such shapes include but are not limited to disks, squares, rectangles or nail-shaped. The medicated device can be applied to the nail and/or nail fold singly or in combination with other medicated devices. A representative medicated device containing salicylic acid is commercially available as Dr. Scholl's Corn Removers, Schering-Plough Healthcare Inc., Memphis Tenn.

The term "film-forming liquid" refers to a vehicle which can assume the shape of a container or flow out of a container, such as solutions of polymeric resins which upon evaporation of the solvent, will form films which hold the salicylic acid against the nail surface.

The term "liquid preparation" refers to a preparation of salicylic acid or a salt, ester or mixture thereof in a film-forming liquid vehicle. The salicylic acid in a liquid preparation is employed in an amount effective to penetrate the nail to reduce and/or control onychomycosis. Such amounts can range from about 6 to about 35 percent by weight of the preparation, more preferably about 10 to about 25 percent by weight, most preferably from about 12 to about 18 percent.

The amount of salicylic acid applied to the nail, either in a film-forming liquid preparation or in the device can range from about two to about 36 milligrams/square centimeters (mg/cm²) of nail, preferably from about 18 to about 36 mg/cm², more preferably about 18 mg/cm².

Optionally, other ingredients can be employed in the topical preparation to assist penetration of salicylic acid into the nail. Such agents can include nail softeners and avulsers, such as urea, sulfhydryl agents and sulfur-based reducing agents such as sodium sulfide, nail penetration enhancers, and occluding agents and/or hydrophillic fillers to promote hydration of the nail.

Medicated devices or liquid preparations containing salicylic acid, can be topically applied to the entire surface of the nail structure, including the region of the cuticle proximal to the nail fold which overlies the growth center of the nail known as the matrix.

The medicated device or liquid preparation can be topically applied according to a regimen effective to reduce or treat onychomycosis. Generally, the preparation can be applied to the nail daily or for intermittent intervals, such as for two to three times per week. The duration of treatment can vary greatly, depending upon the degree of severity of the infection, the part of the body where the nail is being treated, the age of the person, the thickness of the nail, the rate of nail growth and the like. Generally, the toenails of a younger person can be expected to receive treatments up to 6 months, whereas the toenails of an older person can be expected to receive treatment up to about one year. These periods reflect the time required for toenails to completely grow out of the toe. Treatment of fingernails can be expected to be faster, since fingernail growth is approximately twice as fast as toenail growth. Effectiveness of the treatment can be evaluated by the subsidence or disappearance of symptoms. Less severe cases where only part of the distal portion of the nail is infected can be expected to require less time for treatment.

EXAMPLE 1

Medicated disk-shaped devices containing 40% salicylic acid in a plaster preparation are prepared by initially blending salicylic acid with a rubber-based vehicle to form a rubber-based plaster preparation. Using a coating machine with lamination stations, the plaster preparation is coated onto a release liner to form a film (ie. plaster) containing about 13 milligrams of salicylic acid per square centimeter. The film is laminated onto a carrier and prepared as rollstock. The rollstock is diecut into 8 mm diameter medicated disk-shaped devices having a surface area of 0.36 square centimeters and a thickness of 9 mils.

EXAMPLE 2

A zone of inhibition assay is performed on the plaster disks of Example 1 containing 40% salicylic acid. The zone of inhibition is recorded in millimeters (mm) from the outer edge of the disk to the margin of the area where microbial growth occurs. The results are provided in Table 1.

                  TABLE 1                                                          ______________________________________                                                          Diameter of Zone of Inhibition -                                               40% salicylic acid in                                         ORGANISM         plaster preparation                                           ______________________________________                                         Staphylococcus aureus                                                                           12 mm                                                         Escherichia coli 10 mm                                                         Pseudomonas aeruginosa                                                                           9 mm                                                         Staphyloccus epidermidis                                                                        16 mm                                                         Candida albicans 11 mm                                                         Candida parapsilosis                                                                            16 mm                                                         ______________________________________                                    

The results indicate that the medicated disk-shaped devices containing 40% salicylic acid in a plaster preparation exhibit bactericidal/fungicidal activity against the organisms tested.

EXAMPLE 3

Medicated disk-shaped devices containing 40% salicylic acid are die-cut from rollstock prepared by laminating a rubber based plaster preparation containing 40% salicylic acid onto a resin-coated cloth carrier. The medicated devices have a surface area of 0.36 square centimeters. Three disks analyzed for salicylic acid content are found to have 12.72±0.36 mg/cm². These samples represent the initial amount of salicylic acid in the disks at zero hours (initial).

Fingernails of a human subject are selected which do not have holes drilled into them and which are not scraped. Disks are applied to central portion of each of three fingernails. The disks are held in place with a bandage and are removed after either 8, 24, or 48 hours. The disks removed at 24 hours are replaced with four subsequent 24-hour applications.

After contacting the nail, the disks are extracted with tetrahydrofuran and analyzed for salicylic acid by a liquid chromatographic techniques. The amount of salicylic acid released into the nail is calculated from the difference between the amount of salicylic acid initially in the disk and the amount remaining in the disk after contacting with the nail.

The presence of the salicylic acid in fingernails is monitored qualitatively by observing fluoresence using a Wood's light having a short wave ultra-violet (UV) wavelength of 254 nanometers (nm). Results are provided in Table 2.

                  TABLE 2                                                          ______________________________________                                         In Vivo Release of Salicylic Acid                                              into Fingernails from Medicated Devices                                                       Salicylic Acid                                                                              Salicylic Acid                                                    Released from                                                                               Released from                                      Medicated Device                                                                              Medicated Device                                                                            Medicated Device                                   Applied to Nail After                                                                         (mg/cm.sup.2)                                                                               (%)                                                ______________________________________                                         0 hours (initial)                                                                             0.00         0                                                  8 hour application                                                                            1.11          8.7                                               First 24 hour application                                                                     2.86         22.5                                               2nd 24 hour application                                                                       3.17         24.9                                               3rd 24 hour application                                                                       3.50         27.5                                               4th 24 hour application                                                                       1.92         15.1                                               5th 24 hour application                                                                       5.42         44.6                                               ______________________________________                                    

The results indicate that salicylic acid is released into the nails. Based upon zero-order release kinetics, the release rate is relatively constant over time, regardless of the number of applications. Salicylic acid is released into the nails at a mean release rate of 0.14 mg/cm² /hr. The treated nails fluoresce in center of the nail, where the plaster is initially applied, with an intensity proportional to the length of exposure. Fluorescence within the nail is observed even after 5 weeks post-treatment. Five to six weeks after application of the medicated device, the area of fluorescence has moved toward the tip of the nail. 

We claim:
 1. A method for treating onychomycosis without drilling a hole in a nail plate and without daily scraping of the nail, comprising topically administering to the afflicted nail of a human, a medicated device comprising salicylic acid or a salt, ester or mixture thereof in a plaster preparation, wherein said plaster preparation is attached to a carrier and the salicylic acid is present in the plaster preparation in an amount ranging from about 10 to about 80% by weight of the preparation.
 2. The method of claim 1 wherein the salicylic acid is about 20 to about 40% by weight of the preparation.
 3. The method of claim 1 wherein the plaster preparation is self-adhering to the nail.
 4. The method of claim 2 wherein the plaster preparation is self-adhering to the nail.
 5. The method of claim 1 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 6. The method of claim 2 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 7. The method of claim 3 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 8. The method of claim 4 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 9. The method of claim 1 wherein the nail is a toenail.
 10. The method of claim 1 wherein the nail is a fingernail.
 11. A method for treating onychomycosis without drilling a hole in a nail plate and without daily scraping of the nail, comprising topically administering to the afflicted nail of a human, a medicated device consisting essentially of salicylic acid or a salt, ester or mixture thereof in a plaster preparation, wherein said plaster preparation is attached to a carrier and the salicylic acid is present in the plaster preparation in an amount ranging from about 10 to about 80% by weight of the preparation.
 12. The method of claim 11 wherein the salicylic acid is about 15 to about 60% by weight of the plaster preparation.
 13. The method of claim 11 wherein the salicylic acid is about 20 to about 40% by weight of the plaster preparation.
 14. The method of claim 11 wherein the plaster preparation is self-adhering to the nail.
 15. The method of claim 12 wherein the plaster preparation is self-adhering to the nail.
 16. The method of claim 11 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 17. The method of claim 12 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 18. The method of claim 13 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 19. The method of claim 14 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives.
 20. The method of claim 15 wherein the plaster preparation is derived from rubber or acrylic based pressure sensitive adhesives. 